The present invention relates to an apparatus and method for removing particulate impurities from a fluid stream flowing into a bed of discrete solid elements, and more particularly, relates to an improved basket design for removing impurities from hydrocarbon streams flowing into a bed of catalyst particles.
In any process which involves conducting a stream of fluid material, either gas, liquid or a mixture of gas and liquid, through a bed of discrete solid elements or particulate material, the cycle life of the bed itself, for example, a bed of catalyst particles in a chemical reaction zone, i.e., reactor, is a function of the amount of impurities which are entrained in the fluid stream. Since the particulate impurities are filtered out of the stream by the layer of bed material through which the stream enters, when a sufficiently large amount of these particulate impurities accumulate at or near the surface of the bed through which the stream enters, the pressure drop across the bed increases to a level which no longer permits acceptable operation of the bed. Hence, the reactor or the like containing the bed must be shut down.
It has heretofore been proposed to overcome this problem and extend the cycle life of a bed of catalytic particles or the like by providing the bed with a grid of cylindrical wire mesh containers, called "trash baskets," which are placed in the bed with an open end at or near the surface of the bed through which the fluid stream enters. In this way, the fluid stream initially follows the path of least resistance and enters the catalyst bed through the cylindrical wire mesh containers whereupon solid impurities entrained in the fluid are filtered therefrom, for example, by the wire mesh. Only after a significant accumulation of impurities has occurred in the vicinity of the wire mesh containers does the pressure drop across these containers increase to the point where the fluid stream substantially seeks entrance into the catalyst bed via that portion of the bed's surface through which the fluid stream enters which lies between the wire mesh containers, i.e., exposed surface. However, because the initial accumulation of collected impurities occurs in the vicinity of the bottom surface of the cylindrical containers, the collected impurities tend to filter out in a radial direction from the bottom of the containers and effectively close off the entire cross-section of the catalyst bed to the flow of the fluid stream therethrough. Thus, neither the vertical sidewalls of the wire mesh containers nor the exposed surface of the catalyst bed, which is still substantially in its initial clean condition, is effectively utilized as a situs for the entry of the fluid stream. Thus, although the use of the heretofore proposed wire mesh container has to some degree extended the cycle life of a catalyst bed, there still remains a significant portion of the bed which cannot effectively be employed, for example, to filter impurities from the fluid stream.